Windshield wiper



umrso "STATE s PAraNr orsics WINDSHIELD WIPEB Marcellus '1. Flaxman, Ponca City, one, assignor to Union Oil Company of California Angelou, Cali! a corporation of Caiiiomii Application August 1.6, 1943. crial No. 498,881

Claims. (oi. -245) This invention relates to the manufacture oi rubber objects which are to be lubricated with water, such as rubber bearings. window cleaning squeegees, and especially for the purpose of cleaning glass surfaces exposed to the elements such as automobile Windshields which are to be cleared of water due to rain, iog or snow by means of rubber windshield wipers.

The eficiency with which windshield wipers and the like operate is dependent upon the formation of a thin continuous film of water on the glass, or in the case of bearings is dependent upon the iiim oi water on the metal in contact with the rubber hearings.

in the case of windshield wipers, the thinner and more continuous the film of water the better the visibility. While visibility is interfered with by the presence of dirt on a windshield or as a result of scratching caused by the dirt, or as a result of oil scum accumulated from passing motors, I have nevertheless found that the greater proportion of visibility dimculty encountered with automobile Windshields and the like is due to the formation of a scum which appears to be a chemical change upon the glass surface due to the presence of alkaline conditions produced either by alkalinity in the windshield wiper or by atmospheric efiects upon glass. Commercial windshield wiper blades have the characteristic of permitting .the formation of such scum, apparently due to the mentioned alkalinity. The presence of this scum prevents uniform wetting of the gl with water and thereby reduces visibility, and I have found that its removal permits uniform wetting and insures good visibility.

An important object oi the invention is to provide a rubber composition for windshield wipers and the like which will prevent the formation of this scum or will result in its removal when formed, whereby to permit uniform wetting of the glass suriace and good visibility. Another object of the invention is to insure sood formation of water film by means of an agent incorporated in the rubber wiper to reduce the surface tension of the water and insure a good water film.

The invention resides. in rubber compositions and also in molded rubber articles which contain a material having an acidic reaction either to make the rubber body neutral in its chemical reaction, or to render it acid, whereby formation of alkaline scum on glass and the like is prevented or removed, or a material to act as a surface tension depressor and thereby constitute a wetting agent. More specifically, the invention resides in a rubber composition suitable for molding into .Loc'

rubber objects such as windshield wipers which contains a matcrialhaving an acidh reaction either to e neutrality in the rubber r or an acid condition in the rubber body; or containing a wetting agent which will reduce suriace of we when the rubber obicct acts spread the water; or containing both material. The invention also resides in such a rubber containing a le mate which acts both as a wetting agent and to rear the rubber y neutral or mid as indicated.

The agent to be incorporated in m. compound should have a ciently .1 ity so that quantities thereof required for the indicated purposes will not the usual dualities of the rubber amt-- while the are d ired prortiw. e i

As examples of suitable materials which have adequate surface tension dep s as i- 8 law esters of aliphatic dibasic acids which con ionic acid groups, either as the esters a: or salt thereof. A sulionated diic acid available on the hot as Aerosol OT I a duced by a-w erican Cyanamide and cal Cororation, and said to be dioctyl sodium o-succinate, is typical oi many useful synthetic and other surface tension depressing materials. The material also has a reaction acidic to litmus. Its pH is between 6 similar salts and esters such as mentioned in atent No. 2,0,091, salts of sulionated alcohols, d equivalent materials. Neutral or slightly acid wetting agents such as above mentioned are preferred inasmuch as they also impart the neutral or acidic conditions mentioned. Any other comting agents are liquids or solids whose boiling or vaporization point or decomposition point is above the ordinary vulcanization temperat 1 oi around 275 F. to 400 l"., and are otherwise at the vulcanization temperature. The mater! above-mentioned meet these requirements. In the case of the wetting agents they should at least be partly soluble in water so as to be slowly lib,

i. i .1 7. Other wetting agents are ersted when m in contact with water. n

acidic materials shall be those which have the capacityorimpartinganeutraloracidcharacboiling point" as used in the claims is intended to include the decomposition or subliming'temperature of materials that do not boil.

As above indicated, agents which have bothtbe property of causing water to wet glass windshields ormetalbearingsreadilyandthepropertyoi neutralizing or imparting acidic conditions to the rubber composition are the mentioned sulionated di-basic acid esters such as the succinic acid ester, similar esters such as mentioned in Patent No. 2,028,091 such as the sulionated esters oi maleic, glutaric, tartaric. i'umaric and phthalic acids with various alcohols such as octyl, lauryl. iurfuryl, henl. amyl, butyl, cyclohexyl alcohols and the glyools, and salts 01' such esters.

In preparing a rubber composition containing an agent or agents of the type indicated ordinarily about 5% of the agent will be employed. However, smaller proportions possibly as low as 1% may be sufllcient according to the nature of the rubber composition and the activit 01' the particular agent, whereas larger proportions'such' as 10% may be necessary according as the rubber composition and the nature or the agent varies.

One composition which I have: employed consisted of 5% of the mentioned sulionated succinic acid'ester incorporated into an ordinary rubber mix. In this case the composition was about as follows:

Parts by weight Smoked sheet rubber 100 86% Zinc oxide..- 85 23% Sulfur 3 2% Stearic acid 3 2% Accelerator 3 2% Aerosol '1 (dioctyl sodium sulio-suc- This mix was worked up in a rubber mill by addinx the cater to the ordinary rubber mix in the usual way. It was then worked into thin sheets suitable to form windshield wipers and vulcanized for 45 minutes at 292 1'. In the V111- canizing operation, stearic acid (which acts as an accelerator for the vulcanization) is neutralized by reaction with part of the zinc oxide and the rubber mix normally would have an alkaline reaction. However, the suli'onated ester apparently is not aii'ected b the zinc oxide and leaves the composition with an acid reaction. At the same time this agent serves as a wetting agent.

The vulcanized sheets were then formed into laminated windshieldwipers which were em- -ployed tor the purpose of clearing Windshields in actual service in. the usual manner,

Another composition was prepared employing about 5% of benaoic acid. In this particular instanceitwasdesiredtomakeailrmerrubber mixandi'orthatreasonabouthalroithcsinc oxide was replaced with iron oxide according to procedures well known in the rubber making art. This composition was similarly vulcanized and Ionned into windshield wipers which were used in ordinary service. i

In using windshield wiper blades manufactured as above described, it was found that visibility was greatly improved and that as pressure upon the glass-oi the windshield was increased the operation of the blade appeared to become more satisi'actory. In the case of the acid ester. which is partly water soluble, the slightly acidic condition imparted by the resence of the ester performed its function and at the same time the wetting iuncti or the agent was permitted to act because a uiiicient new supply oi the wetting agent became continuousl available due to slight penetrating powers of the water tor the rubber and to the slight wear 0! the blade, tending to expose additional quantities c1 material. Both this blade and the blade made with bensoic acid served to remove scum which interfered with visibility and was already on the windshield, and thereafter to prevent the formation or such a scum, thereby maintaining good visibility conditions during driving in rain and log.

When employing acidic materials, mineral acids are objectionable because oi! their decomposition temperatures and their eifect upon the rubber. water-soluble organic acids. having the characteristics herein described, may be incorporated in the rubber mix either by mixing them directly therewith on the rubber mill, or by preparing strong solutions and adding the solutions to the rubber mix on the rubber mill, the water being driven out in the milling operation thereby distributing the acid uniiormly through the unvulcanized rubber composition. The proportion of these acids used may depend upon the ionization constants. The higher the ionization constant the smaller the amount of acid required for a given rubber mix.

Other compositions ma be made employing any preferred rubber compounding procedure with preferred proportions of materials, various agents within the scope of the claims being added in larger or smaller proportions as may seem appropriate or necessary and in accordance with conditions as above indicated.

Iclaim:- 1. A vulcanized rubber windshield wiper containing a small proportion of a sulionated organic di-basic acid ester.

2. An article according to claim 1 containing basic acid ester. I

5. An article according to claim 4 wherein the ester is dioctyl sodium sulro-succinate.

MARCEILUS T. FLAXMAN. 

